Research On Bi-directional Power Test Supply

The Power Test Supply is applied in power stations, substations and medium-sized industrial enterprises, it not only can be used as standard relay test power supply, but also as a portable power supply, which provide reliable DC power supply for the secondary equipments. With the rapid development of power industry in China, the demands of Power Test Supply in power operation and maintenance testing are increasing grow. Meanwhile, better performance of the power supply is required as well, and the characteristics of high-frequency, intelligent, miniaturized, multi-purpose and high reliability in Power Test Supply has become an important trend.A Bi-directional Power Test Supply is investigated in this paper. Due to the characteristics of bi-directional power flow, this power supply not only can be used as normal Power Test Supply, but also as battery charge/discharge instruments, so it has multifunctional characteristics and widely applications, which can improve equipment utilization and reduce equipment cost. In addition, when it works as battery discharge instruments, the power supply can feedback the power to the grid, which achieve the recycling of energy and meet the subjects of energy saving advocated by society.The total schemes of Bi-directional Power Test Supply is proposed in this paper, and the topologies of single phase Pulse Width Modulated (PWM) reversible rectifier and bi-directional full-bridge DC/DC converter are selected later. In the front stage, the PWM rectifier has lower harmonic and higher power factor. In the behind stage, with an active clamp the converter can achieve hybrid zero-voltage/zero-current switching (ZVZCS) for the buck bridge, while limiting the voltage of switches and realize soft-switching in boost bridge.The fundamental operating principles of PWM reversible rectifier and bi-directional full-bridge DC/DC converter are analyzed in this paper, and the control strategies of PWM rectifier and DC/DC converter under different work conditions are further analyzed. Meanwhile, the effects of active clamp in voltage spike suppress, soft switch optmition,and soft atart in boost full-bridge are analyzed deeply,and the produce method of driving signal for active clamp switch is also analyzed.The principle of cooperative work in two stages is analyzed, and the digital control system is designed later. The design method of the key components such as filter inductance in first stage and high-frequency transformer in second stage are given, and the digital program is also designed. The correctness of design parameters and the feasibility of control strategies are illustrated and verified on simulation.The design method of the key components such as filter inductance in first stage and high-frequency transformer in second stage are given, and the control program based on the dsPIC33F digital controller is also designed. The correctness of design parameters and the feasibility of control strategies are illustrated and verified on Saber simulation.Finally, based on the theoretical analysis and simulation research, the maximum output 250V/5A digital experimental prototype is designed. The experiments show that the two stages can achieve bi-directional power flow with higher efficiency. The PWM reversible rectifier in front stage run with higher power (PF) fator and lower total harmonic distortion (THD). With the active clamp, the switchs in full-bridge DC/DC converter can operate with no spike. The converter can achieve ZVZCS for the buck bridge, while limiting the voltage of switches in the boost bridge. On the other hand, digital control is more convenient in debug stage, and the peripheral control circuit of MCU is simple, so the power supply has good application value.